Ifitaint,
The differences training is only if you wish to fly the "different" type of microlight.
ie If you have flown a three-axis light aircraft (is there any other type!) then there is no "difference in control systems". But if you wished to fly a weightshift microlight, then there would be "differences" training required
However, due to lower inertia etc - and the need to feed my family! - I would recommend some conversion training.